Years ago there was discussion about how libraries were limited by Overdrive depending on library card requirements. Essentially if you don't have a policy of local residents only you get access to a smaller catalog. I don't know if it is still true or not.

My library has a pretty good selection, but I am always surprised when certain authors and books don't even show up under the additional titles to recommend.

Convenience? Despite using my library system liberally and even having its numbers as some of my most commonly called in my contacts, there were times where I wasn't quite able to get what I wanted in a "reasonable" amount of time.